The
British Association, on the contrary, requires the sample to be broken in
small pieces. If the original sample is taken in such fashion as to
include large and small lumps as accurately as possible in the same
proportion as that in which they occur in the main parcel, no error will
be introduced if that sample is crushed to a uniform size, and then
subdivided again; but a small deficiency in gas yield will be produced,
which will be in the consumer's favour. It is not altogether easy to see
the advantage of the British idea of crushing the sample over the German
plan of leaving it alone; because the analytical generator will easily
take, or its parts could be modified to take, the largest lumps met with.
If the sample is in very large masses, and is decomposed too quickly,
polymerisation of gas may be set up; but on the other hand, the crushing
and re-sampling will cause wastage, especially in damp weather, or when
the sampling has to be done in inconvenient places. The British
Association requires the test to be made on carbide parcels ranging
between 1 and 2-1/2 inches or larger, because that is the "standard" size
for this country, and because no guarantee is to be had or expected from
the makers as to the gas-producing capacity of smaller material.
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